Although the medical treatment of central nerve system diseases has been conventionally considered as difficult due to the impossibility of nerve regeneration, the regeneration medicine is recently attracting expectations as a new therapy. Conventionally, a method of transplanting embryonic stem cells or neural stem cells obtained from an embryo brain into the brain has been investigated as the regeneration medicine; however, this method faces immunological rejections, supply limitation of cells, and ethical problems.
As one of therapies for solving such problems, transplantation of bone marrow stromal cells (BMSCs) or mesenchymal stem cells (MSCs) obtained by isolation of bone marrow stromal cells has been proposed. For example, it was reported by Chen et al. in 2000 that a cell therapy of BMSCs into the brain was effective to rat cerebral infarction models (non-patent literature 1), and from then on, use of BMSCs has been recognized as one candidate of cell therapies of central nerve system diseases. BMSCs are easy to be obtained and have a low risk of immunological rejections due to the adaptability to autotransplantation, while causing less ethical problems.
Furthermore, intravenous transplantation of BMSCs has been investigated. Intravenous cell transplantation, which can be achieved by drip infusion as is the case with medicine infusion, is considered as non-filtrating and safer. Curative effects achieved by intravenous cell transplantation have been reported, for example, in non-patent literatures 2 to 6 described below and considered as near to practical application. Bang et el. reported that a clinical test involving intravenous autotransplantation of BMSCs for patients of middle cerebral artery occlusion is already performed, and that cerebellar atrophy and brain function are improved (non-patent literature 6).